Veterans of our Institute

When the main thing is physics

In the spring of 2021, on the eve of the 65th anniversary of the Frank Laboratory of Neutron Physics, we started a series of biographical publications about the Laboratory's staff members. Today, Alexander Vladimirovich STRELKOV, a leading researcher in the research sector for fundamental properties of the neutron at FLNP that began working in the Laboratory in 1960, after graduating from Gorky State University, talks about why he chose physics as his life's work.

- Despite the fact that in my family almost all the men were engaged in physics: four cousins are physicists and much higher in rank than me (all are doctors of science, some of them work at the Kurchatov Institute, the others - at the Lebedev Physical Institute, my uncle is a professor at Moscow State University, he headed the Department of Oscillation Theory), I didn't think about physics at first," Alexander Vladimirovich says. "My father was Head of the Laboratory of Electrophysics of the large plant "Krasnoe Sormovo". He brought home various instruments and showed me physical experiments that greatly influenced my hobbies and future choices. He sometimes even egged me on and suggested that I find an explanation for some effect. For example, to explain the paradox of tea leaves in a glass of tea that A. Einstein once drew attention to. As it is known, in a centrifuge, impurities in a liquid with a lower density are gathered in the centre and with a higher density, they move to the periphery. But with tea leaves that lie at the bottom and are stirred in a glass, it does not work - they should move towards the walls of the glass, but gather in the centre. When the glass stands and the liquid rotates, braking occurs on the walls, vortices are formed, picking up and gathering the tea leaves into a pile at the bottom. I figured out how to test this experimentally: when I hung a glass of tea on a thread and twisted it, the tea leaves scattered to the periphery that explained this paradox.

But my attitude to science as a profession was developed by my school physics teacher Vyacheslav Stepanovich Permitin, who I was very lucky with. He very simply explained to us the basics of physics, explained the most complex things in his fingertips, even quantum mechanics. Moreover, he said: an indivisible elementary particle passes simultaneously through two holes. Sorry, I don't understand it myself, how a particle is also a wave, but experiments confirm it.

And today, I've been working in Dubna for five years. Doorbell. Vyacheslav Stepanovich is standing on the threshold. He arrived without warning and I didn't have a phone yet. He asks, laughing: will you let me in? He came to see me from Moscow, where at the Ministry of Education he was looking for an opportunity to meet with the author of a new physics textbook published at that time, Academician I.K.Kikoin. He showed me a notebook in which he wrote down 50 errors and inaccuracies that he discovered in this textbook. He arrived at the Ministry of Education and they told him: the author of this textbook works in a "closed" institute, you leave everything to us, we will pass it on to him. Kikoin worked at the Kurchatov Institute and I regularly went there for experiments. Vyacheslav Stepanovich, of course, didn't know this, he just stopped by to see me. Through Yakov Abramovich Smorodinsky, I handed over the notebook to Kikoin. About two weeks later, Kikoin's secretary contacted me and conveyed his words: yes, your teacher carefully read our textbook.

Vyacheslav Stepanovich asked me to show him the Institute and tell him what I was engaged in. How to show on Sunday?! I called Head of the Security Department Nikolay Pavlovich Terekhin and explained that my school physics teacher had suddenly come to see me, whether he would be able to visit the Institute. Unexpectedly, he gave permission! And when I told him that the teacher had a prosthesis and had a limp, he even gave us a car. He called security and in the Laboratory we examined the IBR reactor and in building No.1 of DLNP we entered the synchrocyclotron hall, for which he was stopped for a while.

The scientific fate of Alexander Vladimirovich was largely determined by Fedor Lvovich Shapiro, Deputy Director of FLNP from 1959 to 1973. In 1960, he initiated work in the Laboratory to study the Mossbauer effect to experimentally prove the principle of equivalence of gravitational and inertial masses. A.V.Strelkov immediately joined this work. Unfortunately, in a similar experiment, the Americans R.Pound and G.Repke were ahead of our group, demonstrating a shift in the frequency of the gamma quantum in the Earth's gravitational field. In the mid-1960s, A.V.Strelkov participated in experiments at IBR on critical neutron scattering, in which the lack of an anomaly in the diffusion coefficient at the liquid-vapor critical point was shown. And later, with the participation of Alexander Vladimirovich, activities began that go on today - first in the discovery and then in the research of ultracold neutrons (UCN). They opened dramatically. At the height of the holidays, in August 1968, when there were only two weeks left before the shutdown for the reconstruction of the first IBR reactor, thanks to the tenacity and perseverance of F.L.Shapiro and the enthusiasm of his young employees V.I.Lushchikov, Yu.N.Pokotilovsky and A.V.Strelkov, they succeeded to confidently register the phenomenon of confinement of slow neutrons in vessels that was subsequently registered as a discovery.

A fterwards, Alexander Vladimirovich studied the UCN storage anomaly. He carried out his first decisive experiments with colleagues at the most powerful reactor in the Soviet Union at that time in Melekes and later, compiled a list of 16 Soviet and foreign reactors that he visited and he had the opportunity to work on some of them. On the initiative and with the participation of A.V.Strelkov, a UCN production facility was developed at JINR at the powerful pulsed reactor BIGR VNIIEF in Sarov that for the first time demonstrated the possibility of transporting UCN from the reactor in closed cans. Experiments to study the UCN storage anomaly were carried out and the Large Gravitational Spectrometer was developed. It was here that in experiments at the reactor of the Laue-Langevin Institute in Grenoble, heating of UCNs in the low energy area was discovered and the cooling effect of a neutron upon impact with a hot wall was registered. This effect still does not have a satisfactory explanation. At the same time, A.V.Strelkov was engaged in an experiment at the YAGUAR rector at VNIITF in Snezhinsk to observe neutron-neutron scattering, dreaming of implementing an experiment on direct observation of neutron-neutron scattering. Why did he choose physics as his life's work?

- I don't regret at all that I chose this profession, it is very interesting. Of course, I have been guided by my students for a long time. There was even a joke in the laboratory: if you want to become Director of FLNP, come to Strelkov's group. After graduating from university, Valery Shvetsov worked in my group and later, became Director of FLNP. I was the supervisor of his dissertation work, as well as the current Director of the Laboratory Egor Lychagin. Today, our youth complain: it's difficult to study physics, there are no grants in sight, we have to somehow get by and try to continue research. It's sad, but 30 percent of the time they are right. I always remember Fedor Lvovich Shapiro, whose main concern was always only physics and not vanity and politics.

Olga TARANTINA,
photo by Elena PUZYNINA